// Use of this source code is governed by a BSD-style license
// that can be found in the License file.
//
// Author: Shuo Chen (chenshuo at chenshuo dot com)

#ifndef MUDUO_BASE_THREADLOCALSINGLETON_H
#define MUDUO_BASE_THREADLOCALSINGLETON_H

#include "uncopyable.h"

#include <assert.h>
#include <pthread.h>
/***
 * 
 * 线程单例类
 * 
 * **/
NAMESPACE_START
template <typename T>
class ThreadLocalSingleton : noncopyable
{
public:
    ThreadLocalSingleton() = delete;
    ~ThreadLocalSingleton() = delete;

    static T &instance()
    {
        if (!t_value_)
        {
            t_value_ = new T();
            deleter_.set(t_value_);
        }
        return *t_value_;
    }

    static T *pointer()
    {
        return t_value_;
    }

private:
    static void destructor(void *obj)
    {
        assert(obj == t_value_);
        typedef char T_must_be_complete_type[sizeof(T) == 0 ? -1 : 1];
        T_must_be_complete_type dummy;
        (void)dummy;
        delete t_value_;
        t_value_ = 0;
    }

    class Deleter
    {
    public:
        Deleter()
        {
            pthread_key_create(&pkey_, &ThreadLocalSingleton::destructor);
        }

        ~Deleter()
        {
            pthread_key_delete(pkey_);
        }

        void set(T *newObj)
        {
            assert(pthread_getspecific(pkey_) == NULL);
            pthread_setspecific(pkey_, newObj);
        }

        pthread_key_t pkey_;
    };

    static __thread T *t_value_;
    static Deleter deleter_;
};

template <typename T>
__thread T *ThreadLocalSingleton<T>::t_value_ = 0;

template <typename T>
typename ThreadLocalSingleton<T>::Deleter ThreadLocalSingleton<T>::deleter_;

NAMESPACE_END // namespace end
#endif        // MUDUO_BASE_THREADLOCALSINGLETON_H
